Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.86	13.316%	$118.8232	$118.82	$118.80	$118.80
Purchase #2	$228.57	9.420%	$250.1013	$250.10	$250.10	$250.10
Purchase #3	$98.44	12.778%	$111.0187	$111.02	$111.00	$111.00
Purchase #4	$168.43	4.626%	$176.2216	$176.22	$176.20	$176.20
Purchase #5	$63.90	10.566%	$70.6517	$70.65	$70.65	$70.70
Purchase #6	$64.43	12.258%	$72.3278	$72.33	$72.35	$72.30
Purchase #7	$249.84	4.127%	$260.1509	$260.15	$260.15	$260.20
7 purchase totals =	$978.47		$1,059.2952	$1,059.29	$1,059.25	$1,059.30